In the low-pressure casting production of an aluminum wheel, the hump (area A in FIG. 1) at the inner rim is thick, has obvious hot spots, and is a common part of casting defects. The hump is at the distal end for mold filling. When molten aluminum flows to the hump, its temperature has decreased so much that the shrinkage defect occurs due to insufficient feeding capacity of the front end. The casting structure at this part is relatively thick and is located between the inner rim and the rim. It is often impossible to directly implement effective cooling to a mold, resulting in the accumulation of heat, slow solidification of the molten aluminum, coarse crystal grains in the casting, and low mechanical properties. In actual production, the large proportion of waste products caused by unqualified casting of humps has seriously affected the molding quality of the wheels and reduced the success rate of samples delivered to customers.